jimhigh66 wrote:
( I want to build a shallow-water drive for a canoe. A small outboard
dosen't work well -- been there, done that.)
If you google "homemade mudmotor" on about the third page you'll find a
bunch of posts on this subject ( boatdesign.net/fourms/... ). According
to the posts this has been done successfully and unsuccessfully with
2-strokes -- depends on how it's done. But nothing is mentioned about
4-strokes. I've posted a question there but no results yet.
I would think the orientation of the power head would be about the same
for the mudmotor application versus weed trimmer. One possible problem
with a 2-stroke: Exhaust "tuning" can be critical and if you try to quiet
them with an additional muffler I'm not sure what it would do to the
perfomance.

There are some wweed eaters that have a cintrifugal clutch in them of
sorts. I've seen some more expensive types (Stihl) that when the
engine dies the head wil still turn or "coast" i would think that
would work pretty good, seeing one could idle with out the prop end
turning, yet under throttle it would have propulsion. Unlike trying
to start it with the prop in the air, just to drop it down and have
water splatter all over the place and kill the engine too.

I know the battries would be a hassle, but couldn't a decent trolling
motor work?